Datasheet

791
SAM9263 [DATASHEET]
Atmel-6249N-ATARM-SAM9263-Datasheet_14-Mar-16
40.4.9 Type ID Checking
The contents of the type_id register are compared against the length/type ID of received frames (i.e., bytes 13 and
14). Bit 22 in the receive buffer descriptor status is set if there is a match. The reset state of this register is zero
which is unlikely to match the length/type ID of any valid Ethernet frame.
Note: A type ID match does not affect whether a frame is copied to memory.
40.4.10 VLAN Support
An Ethernet encoded 802.1Q VLAN tag looks like this:
The VLAN tag is inserted at the 13
th
byte of the frame, adding an extra four bytes to the frame. If the VID (VLAN
identifier) is null (0x000), this indicates a priority-tagged frame. The MAC can support frame lengths up to 1536
bytes, 18 bytes more than the original Ethernet maximum frame length of 1518 bytes. This is achieved by setting
bit 8 in the network configuration register.
The following bits in the receive buffer descriptor status word give information about VLAN tagged frames:
 Bit 21 set if receive frame is VLAN tagged (i.e. type id of 0x8100)
 Bit 20 set if receive frame is priority tagged (i.e. type id of 0x8100 and null VID). (If bit 20 is set bit 21 is set
also.)
 Bit 19, 18 and 17 set to priority if bit 21 is set
 Bit 16 set to CFI if bit 21 is set
40.4.11 PHY Maintenance
The register EMAC_MAN enables the EMAC to communicate with a PHY by means of the MDIO interface. It is
used during auto-negotiation to ensure that the EMAC and the PHY are configured for the same speed and duplex
configuration.
The PHY maintenance register is implemented as a shift register. Writing to the register starts a shift operation
which is signalled as complete when bit two is set in the network status register (about 2000 MCK cycles later
when bit ten is set to zero, and bit eleven is set to one in the network configuration register). An interrupt is
generated as this bit is set. During this time, the MSB of the register is output on the MDIO pin and the LSB
updated from the MDIO pin with each MDC cycle. This causes transmission of a PHY management frame on
MDIO.
Reading during the shift operation returns the current contents of the shift register. At the end of management
operation, the bits have shifted back to their original locations. For a read operation, the data bits are updated with
data read from the PHY. It is important to write the correct values to the register to ensure a valid PHY
management frame is produced.
The MDIO interface can read IEEE 802.3 clause 45 PHYs as well as clause 22 PHYs. To read clause 45 PHYs,
bits[31:28] should be written as 0x0011. For a description of MDC generation, see the “Network Configuration
Register” on page 799.
40.4.12 Media Independent Interface
The Ethernet MAC is capable of interfacing to both RMII and MII Interfaces. The RMII bit in the EMAC_USRIO
register controls the interface that is selected. When this bit is set, the RMII interface is selected, else the MII
interface is selected.
Table 40-4. 802.1Q VLAN Tag
TPID (Tag Protocol Identifier) 16 bits TCI (Tag Control Information) 16 bits
0x8100 First 3 bits priority, then CFI bit, last 12 bits VID